Ball lapping device

ABSTRACT

A ball lapping device comprises two superimposed lapping discs spaced by a working gap, one of the discs being stationary while the other disc is rotatable and includes concentric lapping grooves in its side facing the other disc. The discs are encompassed by a rotary magazine including a circular guide path for balls to be lapped. A radial recess in the stationary disc connects the working gap with the guide path. In one mode of operation balls on the guide path are deflected by a guide from the guide path into the working gap and after being lapped for one revolution are returned by the guide to the guide path. In a second mode of operation the connection between the guide path and the working gap is closed whereby balls in the grooves are continued to be lapped until they have attained the desired surface finish.

United States Patent on 3,660,942 Messerschmidt 51 9, 1972 [s41 BALLLAPPING DEVICE 3,348,338 10/1967 Messerschmidt ..s|/3 [72] Inventor:Sebastian Messerschmldt, Schonun- I gen/Bavaria, Germany PrimaryExaminer-William R. Armstrong Attorney-Bane, Baxley 8L Spiecens 57]ABSTRACT A ball lapping device comprises two superimposed lapping discsspaced by a working gap, one of the discs being stationary while theother disc is rotatable and includes concentric lapping grooves in itsside facing the other disc. The discs are encompassed by a rotarymagazine including a circular guide path for balls to be lapped. Aradial recess in the stationary disc connects the working gap with theguide path. In one mode of operation balls on the guide path aredeflected by a guide from the guide path into the working gap and afterbeing lapped for one revolution are returned by the guide to the guidepath. In a second mode of operation the connection between the guidepath and the working gap is closed whereby balls in the grooves arecontinued to be lapped until they have attained the desired surfacefinish.

9 Claims, 4 Drawing Figures BALL LAPPING DEVICE The present applicationis .a continuation-in-part application based upon my copendingapplication Ser. No. 789,614 filed Jan. 7, 1969, now abandoned.

The invention relates to a device .for lapping balls between twoconcentric spaced apart discs including grooves in which the balls run,one of said discs being rotary while the other disc is stationary, theballs being alternately guided between and away from the discs.

The balls disposed between the discs are set in motion by the rotationof one disc. As the balls roll along the surfaces of the grooves anddiscs, a sliding movement of varying magnitude is set up whichconstitutes the lapping force. This lapping force, in combination withsuitable lapping agents, such as corundum or the like, causes gradualaltering of a nonround shape of the balls to a substantiallygeometrically perfect spherical shape. However, the cross section of thegrooves tends to change buy its coaction with the surface of the balls,and it is this cross section of the grooves in the lapping disc whichhas a decisive influence upon the shaping of the balls.

DESCRIPTION OF THE PRIOR ART To improve the lapping accuracy, it hasbecome increasingly customary to associate with the lapping devices amagazine, for instance, a ring shaped plate magazine encompassing thelapping discs, in order to increase the number of balls and to improvethe running-in grooves in the lapping discs. To obtain a substantiallyuniform ball size, the balls after each rotation between the lappingdiscs are guided through the magazine from which they are returned,between the lapping discs. The result is a constant alternation asbetween the individual balls and the various grooves in the lappingdiscs. Irrespective of whether with this mode of operation the ballsmove at random when in the magazine or are guided in a continuous seriesthrough the magazine so that they do not change their sequence, all theballs in the machine are nevertheless uniformly processed and allthegrooves in the lapping discs have a substantially uniform and crosssectional shape.

While with this mode of operation, balls which are geometrically roundwith only small tolerances in diameter and very accurately shapedsurfaces can be produced, it has been found that the constant removal ofthe balls from the lapping discs, followed by their reintroduction,causes damage to the surfaces of the balls, even if such damage mayamount to only fractions of one-thousandth of a millimeter.

THE INVENTION According to the invention there is provided a lappingdevice in which the balls are lapped between two concentric superimposeddiscs including grooves in which the balls to be lapped run. One of thediscs rotates while the other disc is held stationary and includes asector-shaped radial recess. The balls are fed to the recess, receivedfrom the recess and guided, after each rotation between the discs,through the magazine. When the balls have become substantially identicalin size and shape, the connection between the sector-shaped recess andthe magazine is interrupted and the balls are caused to rotatecontinuously between the lapping discs until they have the requiredmaximum surface finish.

Interruption of the connection between the sector-shaped recess and themagazine thereby causing the balls to rotate continuously, prevents theballs from knocking against one another outside the lapping discs andthus possibly damaging their surfaces, even if only very slightly.

A further important advantage of the invention as shown by a largenumber of tests is that the surface finish of the balls is decisivelydetermined by the correlation between the groove cross section and theball cross section. This, again presumes the use of balls ofsubstantially uniform diameter or within a very narrow tolerance, sincethis is the only condition by which the necessary correlation betweenthe cross sections of the grooves and the balls is provided. However,once this correlation has been achieved, all that is required is a briefcontinuous rotation of the balls between the lapping discs, while thediscs are closed off for the balls now stored in the magazine.Conveniently, the feed of balls to the magazine is temporarilyinterrupted during this stage of the operation. The lapping discs areagain connected to the magazine for feeding a further supply of balls tothe discs when the balls which now have. a perfect surface polish havebeen removed from the discs. This operation is repeated until the lastball, first processed to the required substantially identical size andshape, has also been given the required maximum surface finish. Thus,the invention prevents damage to the surfaces of the very sensitiveballs precisely during the finishing operation.

Another important feature of the invention is that the finishingoperation is performed in the same lapping device in which the ballshave been preliminarily processed. This ensures an accurate correlationbetween the cross section of the grooves in the lapping discs and theball cross section, thus again providing the best conditions for anoptimal surface polishing operation.

While the invention is particularly suitable for lapping devicesincluding lapping discs rotating around a vertical axis and asubstantially horizontal rotating magazine, it can also be successfullyapplied to lapping devices including different kinds of magazines anddifferent arrangements of the lapping discs.

DETAILED DESCRIPTION OF THE INVENTION In the accompanying drawing apreferred embodiment of the invention is shown by way of illustrationand not by way of limitation.

In the drawing:

FIG. 1 is a plan view upon the lapping device set for alternate travelof the balls between the lapping discs and along the guide path of themagazine;

FIG. 2 is a diagrammatic section along line [1-1] of FIG. 1; FIG. 3 is aplan view of the lapping device but set for continuous lapping of theballs between the lapping discs; and

FIG. 4 is a diagrammatic section taken on line IV-IV of FIG. 3.

Referring now to the figures more in detail the exemplified lappingdevice comprises two coaxially superimposed lapping discs 1 and 5 whichare rotatable relative to each other. As shown, the upper disc 5 isstationary and the lower disc I is rotatable and mounted for thispurpose in a carrier 2 which should be visualized as being driven by asuitable power drive means (not shown). The two discs are spaced apartto define a working gap 23 therebetween. The upper disc 5 is mounted ona carrier 6 which should be visualized as being detachable from thedevice by lifting it. The lower disc has in its side facing the upperdisc three concentric lapping grooves 3 for lapping balls 4 in thegrooves by the relative rotations of the two discs. While three groovesare shown, it should be understood that more or less than three groovescan be used. The cross sectional shape of the grooves is, of course,selected in accordance with the desired dimensions of the balls to belapped. The upper disc includes a radially disposed sectorshaped cut-out7 the outer circumferential width of which may represent an angle ofabout 40.

The two lapping discs 1 and 5 are eccentrically disposed within anannular magazine 8 preferably of the plate type. The rotational axis ofthe magazine is spaced fromthe center axis 9 of the discs by a distancex on the diameter 10 of the magazine as it is shown in FIG. 3. Thusdiameter 10 constitutes an angle bisector for cut-out 7 of disc 5.

The disc 1 is presumed to rotate in counter-clockwise direction as it isindicated by an arrow 12 while the magazine 8 rotates in clockwisedirection as indicated by an arrow 13. Of course, the rotationaldirections of disc 1 and the magazine can be reversed. In some instancesdisc 1 and the magazine may be rotated in the same direction, providedthat a substantial speed differential is maintained.

Magazine 8 has a rotary peripheral outer wall to which is fixedlysecured for joint rotation a ring member 14 which constitutes a circularguide path. The radially inner rim of ring 14 is bordered by astationarily mounted annular wall 16. This wall has in radial alignmentwith the cut-out 7 in the upper stationary disc 5 a circumferentiallyelongate opening 17 as it is clearly shown in FIGS. 1 and 2.

A guide strip 18 is detachably secured to upper stationary disc 5. Theradially inner end 19 of the strip is bent off toward wall 20 of cut-out17, that is, in opposition to the rotational direction of disc 1 and theradially outer end 21 is bent toward magazine wall 15 in the directionopposite to the curvature of bent-off portion 19. A closure member 24 isdisplaceably held by means of suitable retaining means such as guides onthe upper disc 5 to permit selective opening and closing of the outerend of cut-out 7 and thus also of opening 17. Of course, closure strip25 can also be adjustably mounted on inner magazine wall 16.

The lapping magazine as hereinbefore described can be selectivelyoperated in two modes of operation.

According to FIG. 1 the device is set for a mode of operation in whichballs 4 travelling on guide path 14 are deflected at 22 by engagementwith one side of guide strip 18 into the working gap 23 and thus intocoaction with lapping grooves 3. As previously explained, they arelapped while disc 1 rotates in counter-clockwise direction. After havingtravelled through substantially one revolution the balls enter cut-out 7and are now deflected by engagement with guide strip 18 on the oppositeside thereof into guide path 14. After travelling in this guide paththrough about one revolution they are returned at 22 to the working gap.This cycle is repeated as long as the guide strip 18 is inserted intothe device and opening 17 is left open.

For the second mode of operation, guide strip 18 is removed and opening17 is closed by inserting closure strip 24 as it is shown in FIG. 3. Asa result, balls 4 in the grooves in lapping disc 1 remain in thesegrooves for an indefinite number of revolutions of the'disc while ballson guide path 14 travel around in the magazine without being subjectedto lapping action.

Such continuous lapping of the balls is continued until the same hasreached the desired configuration and surface finish.

As it is evident, the balls in the grooves are not likely to hit oneanother with any force whereas balls on guide path 14 may collidethereby causing surface damage however slight. When the lapping of theballs in the mode of FIGS. 3 and 4 is completed the operator may revertto the mode of FIGS. 1 and 2 either for a prolonged period of time orfor only a period of time sufficient to feed a new supply of balls intothe working gap 23 after removing the finished balls by lifting carrier6 and thus also disc 5.

While the invention has been described in detail with respect to acertain now preferred example and embodiment of the invention, it willbe understood by those skilled in the art after understanding theinvention, that various changes and modifications may be made withoutdeparting from the spirit and scope of the invention, and it isintended, therefore, to cover all such changes and modifications in theappended claims.

What is claimed is:

l. A device for lapping balls of rigid material, said device comprisingin combination:

a pair of lapping discs disposed in mutually parallel and spaced apartrelationship, one of the discs having in its side facing the other disca circular groove concentric with the discs, the spacing between thediscs constituting a working gap, the grooved disc being rotary;

an annular magazine encompassing both said discs, said magazine defininga circular guide path for balls to be lapped substantially coplanar withthe grooved side of the rotary disc,

said other disc including in its side facing the grooved disc a radiallydisposed cut-out communicating with said circular uide path to provideaccess for balls from the guide pa of the magazine to the working gapand vice versa;

and

a closure means for selectively opening and closing the connectionbetween the guide path and the working gap.

2. The lapping device according to claim 1 wherein said closure meanscomprises an opening in a wall portion of the magazine facing thecut-out in said other lapping disc, and a closure member for selectivelycovering and uncovering said opening.

3. The lapping device according to claim 2 wherein said other lappingdisc is stationarily mounted, and said closure member is releasablyattached to said stationary disc.

4. The lapping device according to claim 1 and comprising a guide memberdetachably insertable into said cut-out, said guide member substantiallyextending across the radial width of the guide path and across thegrooved side of the rotary disc, substantially bisecting the radialwidth of said cut-out.

5. The lapping device according to claim 4 wherein said magazine andsaid rotary disc are rotatable in opposite directions, balls on saidguide path impacting against one side of said guide member beingdeflected into the working gap and balls in the working gap impactingagainst the other side of the guide member being deflected upon theguide path.

6. The lapping device according to claim 5 wherein said guide member isa guide strip terminating at its end within the guide path in a portionbent in opposition to the rotational direction of the magazine and atits end within the working gap in a portion bent in opposition to therotational direction of the grooved lapping disc.

7. The lapping device according to claim 1 wherein said magazinecomprises two concentric radially spaced walls, the outer one of saidwalls being rotatable and having secured thereto a ring member definingsaid guide path and the inner wall being stationary and including anopening constituting said connection between the guide path and theworking gap.

8. The lapping device according to claim 7 wherein the center axes ofthe discs and the rotational axis of the outer magazine wall areeccentrically disposed, the outer peripheral wall of the rotary lappingdisc and the stationary inner wall of the magazine including wallportions disposed in tangential relationship, said tangentially disposedwall portions including the cut-out in the rotary disc and the openingin the inner magazine wall in radial alignment with each other.

9. The lapping device according to claim 1 wherein the disc facing thegroove is operationally stationary and mounted for lifting out ofcoaction with the grooved disc.

1. A device for lapping balls of rigid material, said device comprisingin combination: a pair of lapping discs disposed in mutually paralleland spaced apart relationship, one of the discs having in its sidefacing the other disc a circular groove concentric with the discs, thespacing between the discs constituting a working gap, the grooved discbeing rotary; an annular magazine encompassing both said discs, saidmagazine defining a circular guide path for balls to be lappedsubstantially coplanar with the grooved side of the rotary disc, saidother disc including in its side facing the grooved disc a radiallydisposed cut-out communicating with said circular guide path to provideaccess for balls from the guide path of the magazine to the working gapand vice versa; and a closure means for selectively opening and closingthe connection between the guide path and the working gap.
 2. Thelapping device according to claim 1 wherein said closure means comprisesan opening in a wall portion of the magazine facing the cut-out in saidother lapping disc, and a closure member for selectively covering anduncovering said opening.
 3. The lapping device according to claim 2wherein said other lapping disc is stationarily mounted, and saidclosure member is releasably attached to said stationary disc.
 4. Thelapping device according to claim 1 and comprising a guide memberdetachably insertable into said cut-out, said guide member substantiallyextending across the radial width of the guide path and across thegrooved side of the rotary disc, substantially bisecting the radialwidth of said cut-out.
 5. The lapping device according to claim 4wherein said magazine and said rotary disc are rotatable in oppositedirections, balls on said guide path impacting against one side of saidguide member being deflected into the working gap and balls in theworking gap impacting against the other side of the guide member beingdeflected upon the guide path.
 6. The lapping device according to claim5 wherein said guide member is a guide strip terminating at its endwithin the guide path in a portion bent in opposition to the rotationaldirection of the magazine and at its end within the working gap in aportion bent in opposition to the rotational direction of the groovedlapping disc.
 7. The lapping device according to claim 1 wherein saidmagazine comprises two concentric radially spaced walls, the outer oneof said walls being rotatable and having secured thereto a ring memberdefining said guide path and the inner wall being stationary andincluding an opening constituting said connection between the guide pathand the working gap.
 8. The lapping device according to claim 7 whereinthe center axes of the discs and the rotational axis of the outermagazine wall are eccentrically disposed, the outer peripheral wall ofthe rotary lapping disc and the stationary inner wall of the magazineincluding wall portions disposed in tangential relationship, saidtangentially disposed wall portions including the cut-out in the rotarydisc and the opening in the inner magazine wall in radial alignment witheach other.
 9. The lapping deVice according to claim 1 wherein the discfacing the groove is operationally stationary and mounted for liftingout of coaction with the grooved disc.